The Section provides expert physical and technological support for radiation treatment. This support consists of routine calibration and quality assurance of all radiation equipment and includes special dosimetry studies, computer-assisted treatment planning, and the design and development of special equipment tailored to special clinical needs. Regular checking of dosimetric and technical set-up aspects of radiation treatment to be continued. 1. An efficiently graded quality assurance program, originally developed for the two Siemens linear accelerators, has been adapated and extended for the three Varian accelerators (Clinacs 4, 18, and 20). A new quality assurance detector using five ionization chambers is being integrated into the OA program. This device will consolidate output, energy and symmetry checks and will be useful for electrons as well as photons. 2. Adaptation of the new radiation equipment has been performed and special supporting equipment for patient treatment has been developed and implemented. 3. The Clinac 4/100, Clinac 18 and Clinac 20 linear accelerators are now fully operational. Preparatory work for total skin and total body irradiation has been completed. Sufficient dosimetric work has been done to allow total body irradiation (TBI) and intraoperative radiotherapy to be performed on both.